CMH Pub 7-7-1 The Siegfried Line Campaign by Charles B. MacDonald. First published 1963.
"The story of the First and Ninth U.S. Armies from the first crossings of the German border in September 1944 to the enemy’s counteroffensive in the Ardennes in December, including the reduction of Aachen, Huertgen Forest, and Operation MARKET-GARDEN in Holland."
GPO number: 008-029-00481-0
Digitized by the U.S. Army Center of Military History: http://www.history.army.mil